Cooling Systems

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Cooling Systems

• Purpose
• Cooling system operation
• Principle components

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Purpose

• To remove surplus or unwanted heat generated by
  engine
• Bring cold engine up to normal operating
  temperature as quickly as possible
• Maintains proper engine operating temperature
  under all conditions
• Liquid cooling systems allow
• A practical way to heat passenger compartment
• Engine manufacturers to design more compact
  engines

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Operation

• Water is circulated through engine by a
  centrifugal water pump
• Water pump is driven off crankshaft by
• Accessory belt
• Timing belt
• Thermostat is closed while engine is cold and
  bypass allows circulation through engine only

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Operation

• Once normal operating temperature is reached,
  thermostat opens and allows coolant circulation
  through radiator
• Heat that is absorbed by coolant in engine, is
  transferred to radiator fins and dissipated to
  ambient air
• Heated water is routed to heater core in
  passenger compartment to provide interior heat

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• The thermostat is closed when the engine is cold,
  and the coolant flows through the bypass passage
  thereby bypassing the thermostat.
• When the thermostat opens, most of the coolant
  flows through the thermostat to the radiator.

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Components

• Water pump
• Thermostat
• Bypass
• Radiator
• Heater core
• Fan and fan clutch
• Hoses and clamps
• Auxiliary coolers
• Pressure cap and overflow system
• Anti-freeze

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Components

• As vehicle speed decreases, additional airflow is
  required to dissipate heat in cooling system
• Additional airflow is provided by engine driven
  (rwd) or electric fans (fwd)
• Engine driven fans use clutches to prevent fan
  operation at high engine speeds or low
  temperatures

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Components

• Hoses are necessary because engine is mounted on
  rubber mounts and designed to move during
  operation
• Hose clamps are necessary to keep coolant from
  leaking out as well as keeping air from leaking
  into cooling system

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Components

• Auxiliary coolers are used to cool and preheat
• Engine oil
• Automatic transmission fluid
• Cooling system reaches normal operating
  temperature much faster than eng/trans
  lubrication systems
• Cooling system is used to dissipate unwanted heat
  collected in eng/trans lubrication systems

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Radiator
Air Conditioning Condenser
Oil Cooler
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Components

• Pressure caps are required to allow operating
  temperatures in excess of 212 deg. F
• Pressurization increases boiling point 3 deg. for
  every 1 psi increase
• Pressurization does not change temperature

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The operation of a typical pressure cap.
Frequently Asked Question
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Components

• Overflow system is designed to capture coolant as
  it expands when it is heated
• As coolant cools and contracts, a pressure
  differential is created and coolant in overflow
  is forced back into radiator
• System must be free of small leaks for proper
  operation

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When an engine overheats, often the coolant in
the overflow container boils.
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Components

• Anti-freeze lowers freezing point of coolant
• Water expands as it freezes and can crack or
  break the engine block and heads
• 50/50 mix of anti-freeze and water drops freezing
  point to -35 deg. F
• Anti-freeze can be mixed up to 70/30
• Anti-freeze also contains chemicals and additives
  that inhibit rust and corrosion

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A radiator cap from a truck that operated with a
low coolant level.
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When checking the cooling system, always inspect
the coolant level in the radiator itself, but
never when the engine is warm. Always allow the
engine to cool to room temperature before
removing the radiator pressure cap.
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Mixing distilled water with antifreeze helps
prevent problems such a lime deposits that could
occur in the cooling system if regular tap water
is used.
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Since the mid 1990s, many vehicle manufacturers
have been using antifreeze coolant that is
silicate and phosphate free. Always check the
owners manual for the specifications for the
recommended engine coolant.
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Antifreeze Types Ethylene glycolThis is the type
that has been used almost exclusively since the
1950s. It is sweet tasting and can harm or kill
animals or pets if swallowed. Propylene
glycolSimilar to ethylene glycol, this type of
coolant is less harmful to pets and animals
because it is not sweet tasting, although it is
still harmful if swallowed. This type of coolant
should not be mixed with ethylene glycol
coolant. Organic acid technology (OAT) antifreeze
coolantThis type does not contain silicates or
phosphates. It is usually orange in color and
was first developed by Havoline (called DEX-COOL)
and used in General Motors vehicles starting in
1996.
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Quick-and-Easy Cooling System Problem
Diagnosis If overheating occurs in slow,
stop-and-go traffic, the usual cause is low
airflow through the radiator. Check for airflow
blockages or cooling fan malfunctioning. If
overheating occurs at highway speeds, the cause
is usually a radiator or coolant circulation
problem. Check for a restricted or clogged
radiator.
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Overheating Can Be Expensive A faulty cooling
system can be a major cause of engine
failure. Engine rebuilders often have nightmares
about seeing their rebuilt engine placed back in
service in a vehicle with a clogged
radiator. Most engine technicians routinely
replace the water pump and all hoses after an
engine overhaul or repair. The radiator should
also be checked for leaks and proper flow
whenever the engine is repaired or
replaced. Overheating is one of the most common
causes of engine failure.